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1.
J Am Chem Soc ; 142(32): 13743-13755, 2020 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-32689791

RESUMO

In many marine organisms, biomineralization-the crystallization of calcium-based ionic lattices-demonstrates how regulated processes optimize for diverse functions, often via incorporation of agents from the precipitation medium. We study a model system consisting of l-aspartic acid (Asp) which when added to the precipitation solution of calcium carbonate crystallizes the thermodynamically disfavored polymorph vaterite. Though vaterite is at best only kinetically stable, that stability is tunable, as vaterite grown with Asp at high concentration is both thermally and temporally stable, while vaterite grown at 10-fold lower Asp concentration, yet 2-fold less in the crystal, spontaneously transforms to calcite. Solid-state NMR shows that Asp is sparsely occluded within vaterite and calcite. CP-REDOR NMR reveals that each Asp is embedded in a perturbed occlusion shell of ∼8 disordered carbonates which bridge to the bulk. In both the as-deposited vaterites and the evolved calcite, the perturbed shell contains two sets of carbonate species distinguished by their proximity to the amine and identifiable based on 13C chemical shifts. The embedding shell and the occluded Asp act as an integral until which minimally rearranges even as the bulk undergoes extensive reorganization. The resilience of these occlusion units suggests that large Asp-free domains drive the vaterite to calcite transformation-which are retarded by the occlusion units, resulting in concentration-dependent lattice stability. Understanding the structure and properties of the occlusion unit, uniquely amenable to ssNMR, thus appears to be a key to explaining other macroscopic properties, such as hardness.

2.
J Struct Biol ; 211(1): 107507, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32304744

RESUMO

Molluscs are one of the most diversified phyla among metazoans. Most of them produce an external calcified shell, resulting from the secretory activity of a specialized epithelium of the calcifying mantle. This biomineralization process is controlled by a set of extracellular macromolecules, the organic matrix. In spite of several studies, these components are mainly known for bivalves and gastropods. In the present study, we investigated the physical and biochemical properties of the internal planispiral shell of the Ram's Horn squid Spirula spirula. Scanning Electron Microscope investigations of the shell reveal a complex microstructural organization. The saccharides constitute a quantitatively important moiety of the matrix, as shown by Fourier-transform infrared and solid-state nuclear magnetic resonance spectroscopies. NMR identified ß-chitin and additional polysaccharides for a total amount of 80% of the insoluble fraction. Proteomics was applied to both soluble and insoluble matrices and in silico searches were performed, first on heterologous metazoans models, and secondly on an unpublished transcriptome of Spirula spirula. In the first case, several peptides were identified, some of them matching with tyrosinase, chitinase 2, protease inhibitor, or immunoglobulin. In the second case, 39 hits were obtained, including transferrin, a serine protease inhibitor, matrilin, or different histones. The very few similarities with known molluscan shell matrix proteins suggest that Spirula spirula uses a unique set of shell matrix proteins for constructing its internal shell. The absence of similarity with closely related cephalopods demonstrates that there is no obvious phylogenetic signal in the cephalopod skeletal matrix.

3.
Acta Biomater ; 80: 176-187, 2018 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-30217589

RESUMO

Bivalve shells are inorganic-organic nanocomposites whose material properties outperform their purely inorganic mineral counterparts. Most typically the inorganic phase is a polymorph of CaCO3, while the organic phase contains biopolymers which have been presumed to be chitin and/or proteins. Identifying the biopolymer phase is therefore a crucial step in improving our understanding of design principles relevant to biominerals. In this work we study seven shells; four are examples of nacroprismatic shells (Alathyria jacksoni, Pinctada maxima, Hyriopsis cumingii and Cucumerunio novaehollandiae), one homogeneous (Arctica islandica), and two are crossed lamellar (Callista kingii, Tridacna gigas). Both intact shells, their organic extracts as isolated after decalcification in acid, and the periostracum overlay have been studied by solid-state CP-MAS NMR, FTIR, SEM and chemical analysis. In none of the shells examined in this work do we find a significant contribution to the organic fraction from chitin or its derivatives despite popular models of bivalve biomineralization which assume abundant chitin in the organic fraction of mollusk bivalve shells. In each of the nacroprismatic extracts the 13C NMR spectra represent similar proteinaceous material, Ala and Gly-rich and primarily organized as ß-sheets. A different, yet highly conserved protein was found in the periostracum covering each of the three nacreous shells studied. The Arctica islandica shells with homogeneous microstructure contained proteins which do not appear to be silk-like, while in the crossed lamellar shells we extracted too little organic matter to characterize. STATEMENT OF SIGNIFICANCE: Hydrophobic macromolecules are structural components within the calcareous inorganic matrix of bivalve shells and are responsible for enhanced materials properties of the biominerals. Prevalent models suggest that chitin is such major hydrophobic component. Contrary to that we show that chitin is rare within the hydrophobic biopolymers which primarily consist of proteinaceous matter with structural motifs as silk-like ß-sheets, or others yet to be determined. Recognizing that diverse proteinaceous motifs, devoid of abundant chitin, can yield the optimized mechanical properties of bivalve shells is critical both to understand the mechanistic pathways by which they regulate biomineralization and for the design of novel bioinspired materials.


Assuntos
Exoesqueleto/química , Bivalves/química , Quitina/química , Substâncias Macromoleculares/química , Ácidos/química , Exoesqueleto/ultraestrutura , Animais , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Quitina/ultraestrutura , Compostos Inorgânicos/análise , Conformação Molecular , Monossacarídeos/análise , Compostos Orgânicos/análise , Proteínas/química , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química
4.
Langmuir ; 31(26): 7183-92, 2015 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-26068530

RESUMO

ß-Casein is a 24 kDa natural protein that has an open conformation and almost no folded or secondary structure, and thus is classified as an intrinsically unstructured protein. At neutral pH, ß-casein has an amphiphilic character. Therefore, in contrast to most unstructured proteins that remain monomeric in solution, ß-casein self-assembles into well-defined core-shell micelles. We recently developed these micelles as potential carriers for oral administration of poorly water-soluble pharmaceuticals, using celecoxib as a model drug. Herein we present deep and precise insight into the physicochemical characteristics of the protein-drug formulation, both in bulk solution and in dry form, emphasizing drug conformation, packing properties and aggregation state. In addition, the formulation is extensively studied in terms of structure and morphology, protein/drug interactions and physical stability. Particularly, NMR measurements indicated strong drug-protein interactions and noncrystalline drug conformation, which is expected to improve drug solubility and bioavailability. Small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) were combined for nanostructural characterization, proving that drug-protein interactions lead to well-defined spheroidal micelles that become puffier and denser upon drug loading. Dynamice light scattering (DLS), turbidity measurements, and visual observations complemented the analysis for determining formulation structure, interactions, and stability. Additionally, it was shown that the loaded micelles retain their properties through freeze-drying and rehydration, providing long-term physical and chemical stability. Altogether, the formulation seems greatly promising for oral drug delivery.


Assuntos
Caseínas/química , Celecoxib/química , Portadores de Fármacos/química , Micelas , Animais , Cápsulas , Bovinos , Liofilização , Modelos Moleculares , Conformação Proteica , Estabilidade Proteica
5.
J Am Chem Soc ; 137(2): 990-8, 2015 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-25523637

RESUMO

Organisms tune the metastability of amorphous calcium carbonates (ACC), often by incorporation of additives such as phosphate ions and water molecules, to serve diverse functions, such as modulating the availability of calcium reserves or constructing complex skeletal scaffolds. Although the effect of additive distribution on ACC was noted for several biogenic and synthetic systems, the molecular mechanisms by which additives govern ACC stability are not well understood. By precipitating ACC in the presence of different PO4(3-) concentrations and regulating the initial water content, we identify conditions yielding either kinetically locked or spontaneously transforming coprecipitates. Solid state NMR, supported by FTIR, XRD, and electron microscopy, define the interactions of phosphate and water within the initial amorphous matrix, showing that initially the coprecipitates are homogeneous molecular dispersions of structural water and phosphate in ACC, and a small fraction of P-rich phases. Monitoring the transformations of the homogeneous phase shows that PO4(3-) and waters are extracted first, and they phase separate, leading to solid-solid transformation of ACC to calcite; small part of ACC forms vaterite that subsequently converts to calcite. The simultaneous water-PO4(3-) extraction is the key for the subsequent water-mediated accumulation and crystallization of hydroxyapatite (HAp) and carbonated hydroxyapatite. The thermodynamic driving force for the transformations is calcite crystallization, yet it is gated by specific combinations of water-phosphate levels in the initial amorphous coprecipitates. The molecular details of the spontaneously transforming ACC and of the stabilized ACC modulated by phosphate and water at ambient conditions, provide insight into biogenic and biomimetic pathways.


Assuntos
Fosfatos de Cálcio/química , Fosfatos de Cálcio/isolamento & purificação , Água/química , Precipitação Química , Cristalização , Estabilidade de Medicamentos , Espectroscopia de Ressonância Magnética
6.
FEBS J ; 280(18): 4652-65, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23863045

RESUMO

(1)H solution NMR spectroscopy is used synergistically with 3D crystallographic structures to map experimentally significant hydrophobic interactions upon substrate binding in solution under thermodynamic equilibrium. Using saturation transfer difference spectroscopy (STD NMR), a comparison is made between wild-type xylanase XT6 and its acid/base catalytic mutant E159Q--a non-active, single-heteroatom alteration that has been previously utilized to measure binding thermodynamics across a series of xylooligosaccharide-xylanase complexes [Zolotnitsky et al. (2004) Proc Natl Acad Sci USA 101, 11275-11280). In this study, performing STD NMR of one substrate screens binding interactions to two proteins, avoiding many disadvantages inherent to the technique and clearly revealing subtle changes in binding induced upon mutation of the catalytic Glu. To visualize and compare the binding epitopes of xylobiose-xylanase complexes, a 'SASSY' plot (saturation difference transfer spectroscopy) is used. Two extraordinarily strong, but previously unrecognized, non-covalent interactions with H2-5 of xylobiose were observed in the wild-type enzyme but not in the E159Q mutant. Based on the crystal structure, these interactions were assigned to tryptophan residues at the -1 subsite. The mutant selectively binds only the ß-xylobiose anomer. The (1)H solution NMR spectrum of a xylotriose-E159Q complex displays non-uniform broadening of the NMR signals. Differential broadening provides a unique subsite assignment tool based on structural knowledge of face-to-face stacking with a conserved tyrosine residue at the +1 subsite. The results obtained herein by substrate-observed NMR spectroscopy are discussed further in terms of methodological contributions and mechanistic understanding of substrate-binding adjustments upon a charge change in the E159Q construct.


Assuntos
Proteínas de Bactérias/química , Dissacarídeos/química , Endo-1,4-beta-Xilanases/química , Geobacillus stearothermophilus/química , Ácido Glutâmico/química , Proteínas de Bactérias/genética , Sítios de Ligação , Cristalografia por Raios X , Endo-1,4-beta-Xilanases/genética , Escherichia coli/genética , Geobacillus stearothermophilus/enzimologia , Geobacillus stearothermophilus/genética , Ácido Glutâmico/genética , Glutamina/química , Glutamina/genética , Interações Hidrofóbicas e Hidrofílicas , Isomerismo , Cinética , Modelos Moleculares , Mutação , Ressonância Magnética Nuclear Biomolecular , Ligação Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Especificidade por Substrato , Termodinâmica , Xilose/química
7.
Nat Mater ; 10(12): 974-9, 2011 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-21983889

RESUMO

Inorganic nanocrystals are attractive materials for solar-cell applications. However, the performance of such devices is often limited by an insufficient alignment of energy levels in the nanocrystals. Here, we report that by attaching two different molecules to a single quantum dot or nanocrystal one can induce electric fields large enough to significantly alter the electronic and optoelectronic properties of the quantum dot. This electric field is created within the nanocrystals owing to a mixture of amine- and thiol-anchor-group ligands. Examining the steady state as well as temporal evolution of the optical properties and the nuclear magnetic resonances of the nanocrystals we found that the first excitonic peak shifts as a function of the capping-layer composition. We also demonstrate that the use of a mixed-ligand-induced electric field markedly enhances the charge generation efficiency in layer-by-layer CdSe-nanocrystal-based solar cells, thus improving the overall cell efficiency.

8.
Proc Natl Acad Sci U S A ; 108(36): 14763-8, 2011 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-21873244

RESUMO

Bioavailable calcium is maintained by some crustaceans, in particular freshwater crayfish, by stabilizing amorphous calcium carbonate (ACC) within reservoir organs--gastroliths, readily providing the Ca(2+) needed to build a new exoskeleton. Despite the key scientific and biomedical importance of the in situ molecular-level picture of biogenic ACC and its stabilization in a bioavailable form, its description has eluded efforts to date. Herein, using multinuclear NMR, we accomplish in situ molecular-level characterization of ACC within intact gastroliths of the crayfish Cherax quadricarinatus. In addition to the known CaCO(3), chitin scaffold and inorganic phosphate (Pi), we identify within the gastrolith two primary metabolites, citrate and phosphoenolpyruvate (PEP) and quantify their abundance by applying solution NMR techniques to the gastrolith "soluble matrix." The long-standing question on the physico-chemical state of ACC stabilizing, P-bearing moieties within the gastrolith is answered directly by the application of solid state rotational-echo double-resonance (REDOR) and transferred-echo double-resonance (TEDOR) NMR to the intact gastroliths: Pi and PEP are found molecularly dispersed throughout the ACC as a solid solution. Citrate carboxylates are found < 5 Å from a phosphate (intermolecular CP distance), an interaction that must be mediated by Ca(2+). The high abundance and extensive interactions of these molecules with the ACC matrix identify them as the central constituents stabilizing the bioavailable form of calcium. This study further emphasizes that it is imperative to characterize the intact biogenic CaCO(3). Solid state NMR spectroscopy is shown to be a robust and accessible means of determining composition, internal structure, and molecular functionality in situ.


Assuntos
Astacoidea/química , Carbonato de Cálcio/química , Quitina/química , Citratos/química , Fosfoenolpiruvato/química , Animais , Astacoidea/metabolismo , Carbonato de Cálcio/metabolismo , Quitina/metabolismo , Citratos/metabolismo , Espectroscopia de Ressonância Magnética , Fosfoenolpiruvato/metabolismo
9.
J Phys Chem B ; 114(18): 5989-96, 2010 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-20397675

RESUMO

The molecular interface between bioorganics and inorganics plays a key role in diverse scientific and technological research areas including nanoelectronics, biomimetics, biomineralization, and medical applications such as drug delivery systems and implant coatings. However, the physical/chemical basis of recognition of inorganic surfaces by biomolecules remains unclear. The molecular level elucidation of specific interfacial interactions and the structural and dynamical state of the surface bound molecules is of prime scientific importance. In this study, we demonstrate the ability of solid state NMR methods to accomplish these goals. L-[1-(13)C,(15)N]Alanine loaded onto SBA-15 mesoporous silica with a high surface area served as a model system. The interacting alanine moiety was identified as the -NH(3)(+) functional group by (15)N{(1)H}SLF NMR. (29)Si{(15)N} and (15)N{(29)Si}REDOR NMR revealed intermolecular interactions between the alanine -NH(3)(+) and three to four surface Si species, predominantly Q(3), with similar internuclear N...Si distances of 4.0-4.2 A. Distinct dynamic states of the adsorbed biomolecules were identified by (15)N{(13)C}REDOR NMR, indicating both bound and free alanine populations, depending on hydration level and temperature. In the bound populations, the -NH(3)(+) group is surface anchored while the free carboxylate end undergoes librations, implying the carboxylate has small or no contributions to surface binding. When surface water clusters grow bigger with increased hydration, the libration amplitude of the carboxyl end amplifies, until onset of dissolution occurs. Our measurements provide the first direct, comprehensive, molecular-level identification of the bioorganic-inorganic interface, showing binding functional groups, geometric constraints, stoichiometry, and dynamics, both for the adsorbed amino acid and the silica surface.


Assuntos
Alanina/química , Dióxido de Silício/química , Química Bioinorgânica , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Compostos Orgânicos , Propriedades de Superfície
10.
J Am Chem Soc ; 130(40): 13425-32, 2008 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-18781749

RESUMO

Biomineralization, particularly the formation of calcium carbonate structures by organisms under ambient conditions, is of vast fundamental and applied interest. Organisms finely control all aspects of the formation of the biomaterials: composition, polymorph, morphology, and macroscopic properties. While in situ molecular-level characterization of the resulting biominerals is a formidable task, solid-state magic angle spinning NMR is one of the most powerful analytical techniques for this purpose. It is employed in this study to elucidate the structure and composition of biogenic calcite formed by Emiliania huxleyi, a unicellular alga distinguished by its exquisitely sculptured calcite cell coverings known as coccoliths. Strain 371 (CCMP) was grown and harvested from (15)N- and (13)C-enriched growth medium, with biosynthetic labeling to enhance the sensitivity of the NMR measurements. Crystalline and interfacial calcite environments were selectively probed using direct and indirect (cross-polarized) (13)C excitation, respectively. Different crystalline environments, in particular structural defect sites at concentrations of up to 1.4% with P and N moieties incorporated, were identified using (13)C rotational-echo double-resonance (REDOR) NMR. REDOR-derived geometrical constraints show that the P and N atoms at the defect sites are 3.2 and 2.3 (+/-0.2) A apart from a crystalline carbon carbonate. The phosphorus and nitrogen moieties within the biogenic calcite are identified as small, non-protonated moieties, attributed to inorganic ions such as PO4(3-) and NO3(-). The carbonates adjacent to these defects are chemically indistinguishable from bulk crystalline carbonates, yet their immediate environments experience reduced rigidity, as reflected by substantial T1((13)CO3(2-)) shortening. Interfacial carbonates, on the other hand, reside in structurally/chemically perturbed environments, as reflected by heterogeneous line broadening. This study is the first to directly unravel evidence on the incorporation of P/N moieties as structural defects within E. huxleyi biogenic calcite, and on the state of the adjacent crystalline carbonates.


Assuntos
Células Eucarióticas/química , Células Eucarióticas/metabolismo , Minerais/química , Minerais/metabolismo , Carbono/química , Carbono/metabolismo , Cristalização , Células Eucarióticas/ultraestrutura , Espectroscopia de Ressonância Magnética , Microscopia Eletrônica de Varredura , Nitrogênio/química , Nitrogênio/metabolismo , Fosfatos/química , Fosfatos/metabolismo
11.
J Magn Reson ; 191(1): 141-7, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-18155935

RESUMO

We present a minor but essential modification to the CODEX 1D-MAS exchange experiment. The new CONTRA method, which requires minor changes of the original sequence only, has advantages over the previously introduced S-CODEX, since it is less sensitive to artefacts caused by finite pulse lengths. The performance of this variant, including the finite pulse effect, was confirmed by SIMPSON calculations and demonstrated on a number of dynamic systems.


Assuntos
Algoritmos , Espectroscopia de Ressonância Magnética/métodos , Compostos Orgânicos/análise , Compostos Orgânicos/química , Processamento de Sinais Assistido por Computador , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
12.
J Am Chem Soc ; 128(45): 14472-3, 2006 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-17090026

RESUMO

The first solid state 29Si NMR of a disilyne, that is, RSiSiR, R = Si(CH(SiMe3)2)2(i-Pr) (1) was measured: delta11 = 364 +/- 20; delta22 = 221 +/- 16 and delta33 = -350 +/- 13; CSA = -643 ppm. These measured values as well as calculations for model disilynes strongly support the description of the Si-Si bond in bent disilynes as a triple bond, although with weakened pi-bonds and a reduced bond order of 2.6.

14.
Bioorg Chem ; 31(4): 306-21, 2003 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12877880

RESUMO

Proton decoupled 31P and 13C solution NMR experiments were applied to mixtures of 3-deoxy-D-manno-2-octulosonate-8-phosphate (KDO8P) synthase, with each of its natural substrates, phosphoenolpyruvate and arabinose-5-phosphate (ASP), and product KDO8P to identify the formation of the enzyme-substrate and enzyme-product complexes. Effects arising from ligand interactions with the enzyme are reported via chemical shifts and line broadening with respect to those of the free ligands in solution, depending on the strength and dynamics of binding under thermodynamic equilibrium conditions. The characterization was done both at low and high field spectrometers, 200 and 500 MHz (1H frequencies), and in cases of 31P NMR measurements, it was demonstrated that only the low field spectrometer is capable of providing direct experimental evidence on the enzyme-ligand interactions. Since both the substrate A5P and the product KDO8P exhibit multiple anomeric forms in solution, evidence for the preference of recognition and binding of particular forms is sought.


Assuntos
Aldeído Liases/química , Aldeído Liases/metabolismo , Isótopos de Carbono , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Pentosefosfatos/química , Pentosefosfatos/metabolismo , Fosfoenolpiruvato/química , Fosfoenolpiruvato/metabolismo , Isótopos de Fósforo , Soluções/química
15.
J Am Chem Soc ; 125(15): 4662-9, 2003 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-12683839

RESUMO

In this report the mode of inhibition of mechanism-based inhibitor (2, K(i) = 0.4 microM) of 3-deoxy-d-manno-2-octulosonate-8-phosphate synthase (KDO8PS), which was designed to mimic the combined key features of its natural substrates arabinose-5-phosphate (A5P) and phoshoenolpyruvate (PEP) into a single molecule, was investigated. Our earlier solid-state NMR observations identified the inhibitor to bind in a way that partly mimics A5P, while the phosphonate moiety of its PEP-mimicking part exhibits no interactions with enzyme residues. This result was apparently in disagreement with the competitive inhibition of 2 against PEP and with the later solved crystal structure of KDO8PS-2 binary complex identifying the interactions of its PEP-mimicking part with the enzyme residues that were not detected by solid-state NMR. To solve this discrepancy, further solid-state REDOR NMR and (31)P solution NMR experiments were applied to a variety of enzyme complexes with the substrates and inhibitor. In particular, a novel frequency-selective REDOR experiment was developed and applied. Integration of the solution and solid-state NMR data clearly demonstrates that under conditions of stoichiometric enzyme-ligand ratio at thermodynamic equilibrium (a) PEP binding is unperturbed by the presence of 2 and (b) both PEP and 2 can bind simultaneously to the synthase, i.e., form a ternary complex with PEP occupying its own subsite and 2 occupying A5P's subsite. The latter observation suggests that under the conditions used in our NMR measurements, the inhibition pattern of 2 against PEP should have a mixed type character. Furthermore, the NMR data directly demonstrate the distinction between the relative binding strength of the two moieties of 2: enzyme interactions with PEP-mimicking moiety are much weaker than those with the A5P moiety. This observation is in agreement with KDO8PS-2 crystal structure showing only remote contacts of the phosphonate due to large structural changes of binding site residues. It is concluded that these phosphonate-enzyme interactions evidenced by both (31)P solution NMR and X-ray are too weak to be preserved under the lyophilization of KDO8PS-2 binary complex and therefore are not evidenced by the solid-state REDOR spectra.


Assuntos
Aldeído Liases/antagonistas & inibidores , Inibidores Enzimáticos/química , Ressonância Magnética Nuclear Biomolecular/métodos , Pentosefosfatos/química , Fosfoenolpiruvato/análogos & derivados , Aldeído Liases/metabolismo , Sítios de Ligação , Ligação Competitiva , Inibidores Enzimáticos/metabolismo , Inibidores Enzimáticos/farmacologia , Pentosefosfatos/metabolismo , Fosfoenolpiruvato/química , Fosfoenolpiruvato/metabolismo , Fósforo/química
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